What Does the Milky Way Weigh? Hubble and Gaia Investigate

This illustration shows the fundamental architecture of our island city of stars, the Milky Way galaxy: a spiral disk, central bulge, and diffuse halo of stars and globular star clusters. Not shown is the vast halo of dark matter surrounding our galaxy.

We can’t put the whole Milky Way on a scale, but astronomers have been able to come up with one of the most accurate measurements yet of our galaxy’s mass, using NASA’s Hubble Space Telescope and the European Space Agency’s Gaia satellite.

The Milky Way weighs in at about 1.5 trillion solar masses (one solar mass is the mass of our Sun), according to the latest measurements. Only a tiny percentage of this is attributed to the approximately 200 billion stars in the Milky Way and includes a 4-million-solar-mass supermassive black hole at the center. Most of the rest of the mass is locked up in dark matter, an invisible and mysterious substance that acts like scaffolding throughout the universe and keeps the stars in their galaxies.

Earlier research dating back several decades used a variety of observational techniques that provided estimates for our galaxy’s mass ranging between 500 billion to 3 trillion solar masses. The improved measurement is near the middle of this range.

“We want to know the mass of the Milky Way more accurately so that we can put it into a cosmological context and compare it to simulations of galaxies in the evolving universe,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “Not knowing the precise mass of the Milky Way presents a problem for a lot of cosmological questions.”

On the left is a Hubble Space Telescope image of a portion of the globular star cluster NGC 5466. On the right, Hubble images taken ten years apart were compared to clock the cluster’s velocity. A grid in the background helps to illustrate the stellar motion in the foreground cluster (located 52,000 light-years away). Notice that background galaxies (top right of center, bottom left of center) do not appear to move because they are so much farther away, many millions of light-years. 

The new mass estimate puts our galaxy on the beefier side, compared to other galaxies in the universe. The lightest galaxies are around a billion solar masses, while the heaviest are 30 trillion, or 30,000 times more massive. The Milky Way’s mass of 1.5 trillion solar masses is fairly normal for a galaxy of its brightness.

Astronomers used Hubble and Gaia to measure the three-dimensional movement of globular star clusters — isolated spherical islands each containing hundreds of thousands of stars each that orbit the center of our galaxy.

Although we cannot see it, dark matter is the dominant form of matter in the universe, and it can be weighed through its influence on visible objects like the globular clusters. The more massive a galaxy, the faster its globular clusters move under the pull of gravity. Most previous measurements have been along the line of sight to globular clusters, so astronomers know the speed at which a globular cluster is approaching or receding from Earth. However, Hubble and Gaia record the sideways motion of the globular clusters, from which a more reliable speed (and therefore gravitational acceleration) can be calculated.

The Hubble and Gaia observations are complementary. Gaia was exclusively designed to create a precise three-dimensional map of astronomical objects throughout the Milky Way and track their motions. It made exacting all-sky measurements that include many globular clusters. Hubble has a smaller field of view, but it can measure fainter stars and therefore reach more distant clusters. The new study augmented Gaia measurements for 34 globular clusters out to 65,000 light-years, with Hubble measurements of 12 clusters out to 130,000 light-years that were obtained from images taken over a 10-year period.

When the Gaia and Hubble measurements are combined as anchor points, like pins on a map, astronomers can estimate the distribution of the Milky Way’s mass out to nearly 1 million light-years from Earth.

“We know from cosmological simulations what the distribution of mass in the galaxies should look like, so we can calculate how accurate this extrapolation is for the Milky Way,” said Laura Watkins of the European Southern Observatory in Garching, Germany, lead author of the combined Hubble and Gaia study, to be published in The Astrophysical Journal. These calculations based on the precise measurements of globular cluster motion from Gaia and Hubble enabled the researchers to pin down the mass of the entire Milky Way.

The earliest homesteaders of the Milky Way, globular clusters contain the oldest known stars, dating back to a few hundred million years after the big bang, the event that created the universe. They formed prior to the construction of the Milky Way’s spiral disk, where our Sun and solar system reside.

“Because of their great distances, globular star clusters are some of the best tracers astronomers have to measure the mass of the vast envelope of dark matter surrounding our galaxy far beyond the spiral disk of stars,” said Tony Sohn of STScI, who led the Hubble measurements.

The international team of astronomers in this study are Laura Watkins (European Southern Observatory, Garching, Germany), Roeland van der Marel (Space Telescope Science Institute, and Johns Hopkins University Center for Astrophysical Sciences, Baltimore, Maryland), Sangmo Tony Sohn (Space Telescope Science Institute, Baltimore, Maryland), and N. Wyn Evans (University of Cambridge, Cambridge, United Kingdom).

Selective Mutism: an Often Misunderstood Diagnosis

Kids with selective mutism often chat happily at home and with family members, but they don’t speak at all or talk very little in other settings like school.

WHEN WE THINK OF anxious children, we might think of kids clinging to their parents at drop-off time or terrified by clowns at birthday parties. But there’s another kind of anxiety that affects young children that is much less understood, even amongst pediatricians and mental health professionals, which delays diagnosis and intervention.

Selective mutism is an anxiety disorder in which a child who is talkative at home is unable to speak in other settings. Children with selective mutism often chat happily at home but don’t speak at all or to a very limited extent in places like school, with friends or even extended family. A child with SM may know all the words to a song at school but be completely frozen while everyone sings along. He might love playing with his friends, but never utter a word on a play date. Children with selective mutism frequently talk with family they see often but are silent or manage only a whisper when aunts and uncles visit. The child may nod, point or gesture, and even play along, but not verbalize when asked a question.

SM can often take a while to be detected because the child speaks freely at home and therefore the parent may have no idea she hasn’t uttered a word at preschool. Teachers may assume the child is just as quiet at home, so the parents must be aware of it. A very well-intended teacher may mislabel the child as “just shy,” and months can pass with the child silent in the classroom and on the playground. Children with SM may get hurt at school and be unable to tell the teacher, and they may wet themselves when they can’t ask to use the bathroom.

Oftentimes, teachers or other adults think that given time, the nonverbal child will warm up and “grow out of it.” Parents who suspect a problem might share their concerns with their pediatrician, only to be told that the child will talk eventually.

Children who have selective mutism can sometimes talk to peers but not adults, or vice versa, which is quite perplexing and can contribute to another damaging myth: that the child is defiant or controlling. Like other anxiety disorders, the fearful situation doesn’t always make sense to the layperson. Children with SM most often want to speak but feel they can’t. Many children I have worked with have shared later on that they felt their words were stuck. One little girl said she had felt her mouth was “super-glued.” A parent explained the disorder as “stage fright about talking.”

It’s not clear exactly how children with SM develop the disorder, but like other anxiety disorders, it’s often a combination of biology and environment. In other words, children with SM might have at least one parent who has a history of anxiety, so this can contribute to some biological predisposition toward anxiety. Additionally, the environment plays a role in shaping the disorder. In essence, when a child with SM is asked a question and doesn’t answer, a teacher or neighbor will back off because the child seems uncomfortable, or a parent or sibling will answer for the child. This ends up creating a cycle of avoidance, which can be hard to break.

The good news is that selective mutism is treatable, and the earlier it’s diagnosed the better. If a parent suspects selective mutism and the pediatrician tells the parent, “Don’t worry, she’s just shy,” it’s helpful to share some resources with the pediatrician about the disorder or offer some other details about the child (e.g. she hasn’t spoken all year at school). Caregivers should feel listened to and taken seriously, since they know their child best.

The most effective treatment for children with anxiety disorders is cognitive behavioral therapy. In the case of SM, the therapy uses techniques that prompt speech and then reinforce successful speaking experiences with lots of what’s called labeled praise, or specific praise for a desired behavior, such as saying, “Thanks for telling me” or “Great brave talking.” That’s in addition to small incentives or rewards, like a toy or prize for practicing talking with the parent in front of a new person or talking to a teacher. Children find their voices by being praised for “brave talking.” It may start with a whisper or a single word but, once unlocked, these children become enthusiastic and outgoing communicators.

Families become part of the treatment, as they help their kids emerge from silence by encouraging small acts of bravery. At the Child Mind Institute, we teach parents the skills kids are learning in therapy and help them look for opportunities to reinforce those skills at home. We use generalization, which means taking therapy “on the road” – we go to stores and other places in the community to help the child practice. Ordering their favorite flavor at the ice cream store is a thrilling victory for these kids. Working with the child’s teachers is important to help them continue progressing in the classroom. You can also check out resources online provided by the nonprofit Selective Mutism Association, part of the Childhood Anxiety Network, and learn more about the disorder at the selectivemutism.org.

Selective mutism may be a lesser-known disorder, but it’s real and very treatable. Once we recognize that these children are more than “just shy,” it’s remarkable to see them find their voices, and show the world who they are.

Does Your Child Have an Anxiety Disorder or a Phobia?

Some children generally do well at home but struggle with anxiety in certain situations, like when they’re around peers at school.

FEAR CAN BE A HELPFUL emotion, particularly for children who are learning to navigate the world. Feeling afraid lets them know when they are in danger and helps them respond.

On the other hand, many children today struggle with anxiety that goes beyond what’s considered normal and healthy. The key is identifying when your child’s fear has changed from productive to harmful. The first step is to understand the different types of anxiety. These include:

  • Generalized anxiety.
  • Situational anxiety and phobias.
  • Social anxiety.

Generalized Anxiety

Generalized anxiety makes your child feel uneasy and nervous about the future. It can refer to worries about everyday issues, such as schoolwork, managing relationships and performing well in extracurricular activities.

Your child needs some anxiety to be motivated to get things done. This is called healthy or productive anxiety. For example, healthy anxiety is what prompts your child to stop watching YouTube videos and start preparing for an upcoming test.

But sometimes anxiety persists, even when it’s no longer helpful. It can get in the way of your child’s life and ability to function.

Situational Anxiety and Phobias

Some kids only struggle with anxiety in very specific circumstances. This is called situational anxiety. For example, your child may have anxiety only in dark rooms at night.

If your child keeps avoiding a situation due to fear of experiencing situational anxiety – or endures the situation and suffers intense distress – he or she may have developed a phobia. Although a child may think of the situation itself as dangerous, what the child is really afraid of are the feelings of fear and panic that he or she associates with that situation.

Phobias can make your child’s life difficult due to the extreme effort the child puts into avoiding triggering situations. The more places where your child has feelings of anxiety, the more situations the child avoids. Kids can get stuck in a cycle of fear and anxiety that reinforces phobias. By feeling a short-term sense of relief when they avoid the situation, they “train” their bodies that avoidance is the best strategy. The world becomes smaller and scarier.

Social Anxiety

Many people think phobias are only about fearing things like spiders (arachnophobia) or small spaces (claustrophobia). But for many children, it’s common to struggle with social phobia, also known as social anxiety.

Social anxiety involves experiencing anxiety, fear or panic in situations where other people are watching or paying attention. Kids with social anxiety dread having other people even notice if their voice is shaky or their hands are trembling. They are terrified of making a mistake or appearing weak in front of others. Studies have shown that some personality traits, such as shyness, introversion and perfectionism, put a child at higher risk for developing social anxiety.

Kids with social anxiety struggle with two main categories of situations: performance situations and interactive situations; and they often go together. Some children fear both types of situations. Children who fear performance situations find it difficult to do any kind of public speaking, even answering questions in class or giving a presentation. They may fear participating in a competition or sporting event. Those who fear interactive situations may experience heightened anxiety at social gatherings, such as birthday parties, meetings, lunch and recess. They may dread talking through a conflict with a peer, initiating conversations or even going out with a group of friends.

What Your Child May Be Experiencing

The way to help children manage excess fear and unhealthy anxiety is to teach them to understand what’s happening when they are caught in a cycle of fear and anxiety, and provide them with skills to cognitively reframe triggering situations as they work to calm down their bodies.

The cycle of fear and anxiety has three components:

  • Physical feelings.
  • Automatic thinking.
  • Behaviors.

The cycle can begin with any one of the three components and expand to the other two. For example, a child may first notice a racing heartbeat, and then start to think, “I can’t do this; I’m too scared.” Or, a child may be thinking, “I have to be perfect; I can’t mess up,” and then suddenly a bout of shaking and trembling begins. Or perhaps the child was unable to do something, like wear a usual “lucky shirt” on the day of a test, and this simple change in what the child does (or doesn’t do) – the behavior – leads to feelings of dread and thoughts of doom.

There are many common physical symptoms your child may experience in scary situations. They might have weak legs, shaky hands or a trembling voice. It may be hard to swallow or catch a satisfying breath. Some kids feel dizzy and numb, almost as if they were floating above their own body. Other physical symptoms include rapid heartbeat, chest discomfort, dry mouth, stomach pain or a choking sensation.

Too much anxiety can even lead to a panic attack, when the child experiences an intense rush of fear – even though there isn’t an actual life-threatening danger – along with multiple physical symptoms.

A child prone to anxiety has a brain that automatically fills with negative thoughts that reflect black and white thinking – or very rigid, inflexible ways of looking at the world. These negative thoughts distort reality and make your child feel far more anxious. It takes some practice to identify these negative thoughts. They often assume catastrophic outcomes – or that the worst will happen: “I will mess up and cry in front of everyone and lose all my friends.” These thoughts feed into the cycle of fear and anxiety.

What You Can Do

First, take a moment to recognize that you’re not alone in parenting a child with anxiety. It can feel overwhelming when your child screams, refuses to go to school or is unable to transition through their daily activities. The hopeful news is that anxiety is one of the most treatable psychological conditions. The first step is to get a referral to a psychologist or social worker who specializes in childhood anxiety. Your pediatrician or family doctor can help you with this.

In addition to seeking help from a therapist or social worker for the anxious child, parents can benefit from joining support groups or speaking with a licensed psychologist to work through their own mounting anxiety and frustration about the child’s situation.

Through practice in therapy and at home, one of the most important techniques your child can learn to master anxiety involves replacing automatic negative thoughts with positive coping thoughts. Some people refer to this dialogue as positive self-talk.

For example, if your child reports thinking, “I’m going to embarrass myself in front of everyone,” help the child identify this negative thought and replace it with, “These are just thoughts, not reality. Just because I fear something doesn’t make it true. Even when I make a mistake, people still care about me.”

The coping thoughts should be realistic and meaningful; if your child doesn’t believe them, the coping thoughts won’t be effective. Try to think of the most accurate outcome or explanation for the situation, not necessarily the most positive. For a child who struggles socially at recess, this self-talk might be, “Even if I’m not invited to be part of a game with the popular kids, I can find something to do, and I will get through recess. I’ve been successful at talking with a couple new friends, so maybe I’ll look for them today.”

Two excellent forms of therapy that can help your child change unhealthy thought patterns are cognitive behavioral therapy, and acceptance and commitment therapy. You can discuss these options with your child’s therapist and learn how to support your child at home. Relaxation training, such as abdominal breathing, meditation and progressive muscle relaxation, can also help ease your child’s physical symptoms of anxiety.

In addition, there are a variety of medicines that have proven effective in helping to manage the symptoms of pediatric anxiety disorders, especially when used in combination with talk therapy.

If you are concerned that your child is overly anxious, remember that there is help available, and it will eventually get better. Your child (and you) can get through this with support.

Gordon, Paul Helps Rockets Top Mavericks 94-93

Houston Rockets guard Eric Gordon (10) sprints to the basket past Dallas Mavericks forward Dirk Nowitzki, left rear, as Austin Rivers (25) and Devin Harris, right, watch in the first half of an NBA basketball game in Dallas, Sunday, March 10, 2019.

Gordon scores 26 points, Paul gets key block as Rockets beat Mavericks 94-93 for 8th straight win.

This time, James Harden was reduced to a supporting role for the Houston Rockets.

Eric Gordon and Chris Paul led the way.

Gordon scored 26 points and Paul blocked Jalen Brunson’s jumper in the final seconds, sending the streaking Rockets to a 94-93 victory over the Dallas Mavericks on Sunday.

Harden was saddled by foul trouble and finished with 20 points in Houston’s eighth straight win, 16 below his season average. The reigning NBA MVP led the Rockets in scoring in his previous 43 games for the league’s longest such streak since Michael Jordan’s 66-game run ended in 1988, according to STATS.

“We’ve had a lot of games where it was ugly and we lost earlier in the season,” Harden said. “But we’ll take the ugly win.”

In a matchup of teams going in opposite directions in the Western Conference, Dallas pushed its in-state rival to the end. After Harden missed a runner with 8.9 seconds to play, the Mavericks had a chance to win.

Coach Rick Carlisle opted to let it play out and rookie Luka Doncic rushed the ball up court. As three Rockets converged on him, Doncic found Brunson on the right wing, but Paul recovered to make a clean block on Brunson’s running 14-footer at the buzzer.

“I read (Doncic) and knew he was going to throw it to Jalen,” Paul said. “Jalen didn’t have enough time to do anything else but shoot it. If he pump-faked it, I’m in trouble. But then, he might not have had enough time to get the shot off.”

Brunson said he liked Carlisle’s decision to not use a timeout.

“It just shows that Coach trusts us, and obviously we want the ball in Luka’s hands,” Brunson said. “He made an unselfish play. I just have to knock it down.”

Gordon snapped a tie with a layup with 3:42 left, and P.J. Tucker’s 3-pointer put Houston up by five with 1:29 remaining. Dwight Powell’s dunk cut the lead to one with 31 seconds left.

Doncic had 19 points and a career-high 15 rebounds for Dallas, and Brunson finished with 18 points. The Mavericks lost for the 10th time in 11 games.


Harden picked up his fifth personal 20 seconds into the second half when Doncic took a charge. He re-entered with 3:03 left in the third and converted a three-point play and then a 3-pointer to put the Rockets up 79-70.

Harden had scored 30 or more points in 47 of his 61 games this season, including 37 of the last 38 entering Sunday.

“I can’t be aggressive on both ends of the floor,” Harden said of his foul trouble. “In the back of my mind, I’m conscious and keep thinking about it. But that’s what you got a team for.”


Doncic limped off the court for a timeout with 4:17 to play, but he stayed in the game. Carlisle said he either banged his knee or landed on it awkwardly.

“The hope is that it’s not serious,” Carlisle said. “We will know more tomorrow.”

Doncic wasn’t available after the game.


Dallas star Dirk Nowitzki scored six points. He needs 35 more to pass Wilt Chamberlain for sixth place on the NBA’s career scoring list.

Nowitzki did not play in the second half, something Carlisle called “a coach’s decision because the matchups were very difficult.”


Rockets: Clint Capela had 17 points and 12 rebounds. … Coach Mike D’Antoni said Kenneth Faried would return to the lineup Monday after missing five games with a left hip contusion, and Nene would rest on the second half of the back-to-back.

Mavericks: Maxi Kleber returned after missing the last two games with left knee trouble. He had 10 points and a career-high 11 rebounds. He also was a primary defender on Harden, frustrating the guard into a 7-for-25 shooting performance.

Lisa Vanderpump Says Her Friendship With Kyle Richards Is ‘Finished’ in the Wake of Puppygate

Kyle Richards and Lisa Vanderpump are seen departing the Jacob Javits Center on May 14, 2015 in New York City.

Lisa VanderpumpOpens a New Window. wrote in her latest Bravo blog postOpens a New Window. that her friendship with Kyle Richards Opens a New Window. is “finished” in the wake of Puppygate.

The restaurateur and animal activist, 58, explained that the last year “has been extraordinarily challenging” as she’s dealt with her brother Mark’s suicide.

“I admit I floundered – I didn’t cope – as I wallowed in the depths of depression, having some good days and many bad,” the Vanderpump Rules star admitted of her distance from her costars.

She then addressed the confrontation between her, her husband, Ken Todd, and Richards, 50, after the former child star came to her house to encourage her to talk to the other women. They ended up in a heated argument and Todd kicked Richards out after she accused his wife of lying.

“For me to put my hand to God and swear on my children’s life and still have my friend disbelieve me is unacceptable. I assure you, if any of my friends were as vociferous in their statement of innocence, holding up their children’s life … guess what? I would believe them,” Vanderpump wrote. “That is where the show started but is ultimately where our friendship finished.”Everything We Know About ‘The Real Housewives of Beverly Hills’ Season 9

She then went into an in-depth explanation of the Puppygate scandal that has taken center stage in season 9 after Dorit KemsleyOpens a New Window. gave away a puppy that she’d adopted from Vanderpump’s charity and the dog, named Lucy Apple Juicy, ended up in a kill shelter.

Soon Teddi Mellencamp and Richards got involved. Lisa Rinna opens a New Window. later waded into the mess and accused Vanderpump of tricking her and the other housewives into appearing in scenes about the canine drama to help her launch her Vanderpump Dogs spinoff series.

Explaining that she and her employees were horrified that the dog, who’d been born and bottle-fed at her facility had been discarded, Vanderpump admitted that “feelings were running high.”

“I sent Dorit a text urging her to get in front this issue,” Vanderpump wrote in her blog post, adding, that she didn’t “believe for one minute that Dorit would’ve knowingly left the puppy in a shelter, but she was guilty of a careless choice.”

Saying that she doesn’t “give a damn at this point,” and instead is focusing on the work of her foundation, Vanderpump admitted that she hasn’t watched any of the episodes, “as I have decided not to revisit a painful time in my life.”

She added that the housewives’ trip to the Bahamas “was supposed to be a brief respite” but instead was “an emotional nightmare that pulled me even deeper.”

She ended her post by encouraging fans to keep watching this season.

“And always remember, ‘I am passionate about dogs…’ You know the rest,” she concluded. “And to my castmates, I will ‘see you next Tuesday.’”