Stars Archives

February 15, 2024February 15, 2024 by Carolyn Collins Petersen

Even Stars Like the Sun Can Unleash Savage Flares in Their Youth

Artist's concept of the flare that burst out from the young nearby star HD 283572. The flare was detected by the Submillimeter Array on Mauna Kea, in Hawai'i. Credit: CfA/Melissa Weiss.

Why would a young Sun-like star suddenly belch out a hugely bright flare? That’s what astronomers at Harvard Smithsonian Astrophysical Observatory want to know after they spotted such an outburst using a sensitive submillimeter-wave telescope. According to Joshua Bennett Lovell, leader of a team that observed the star’s activity, these kinds of flare events are rare in such young stars, particularly at millimeter wavelengths. So, what’s happening there?

February 15, 2024February 15, 2024 by Evan Gough

Even if We Can’t See the First Stars, We Could Detect Their Impact on the First Galaxies

Population III stars were the Universe's first stars. They were extremely massive, luminous stars, and many of them exploded as supernovae. How did they shape the early galaxies? Image Credit: DALL-E — Population III stars were the Universe's first stars. They were extremely massive, luminous stars, and many of them exploded as supernovae. Image Credit: DALL-E

For a long time, our understanding of the Universe’s first galaxies leaned heavily on theory. The light from that age only reached us after travelling for billions of years, and on the way, it was obscured and stretched into the infrared. Clues about the first galaxies are hidden in that messy light. Now that we have the James Webb Space Telescope and its powerful infrared capabilities, we’ve seen further into the past—and with more clarity—than ever before.

The JWST has imaged some of the very first galaxies, leading to a flood of new insights and challenging questions. But it can’t see individual stars.

How can astronomers detect their impact on the Universe’s first galaxies?

February 2, 2024February 2, 2024 by Evan Gough

A Super-Earth (and Possible Earth-Sized) Exoplanet Found in the Habitable Zone

Artist depiction of the surface of a super-Earth orbiting a red dwarf. Credit: ESO/M. Kornmesser

Astronomers have found a new Super-Earth orbiting an M-dwarf (red dwarf) star about 137 light-years away. The planet is named TOI-715b, and it’s about 1.55 Earth’s radius and is inside the star’s habitable zone. There’s also another planetary candidate in the system. It’s Earth-sized, and if it’s confirmed, it will be the smallest habitable zone planet TESS has discovered so far.

February 2, 2024February 2, 2024 by Brian Koberlein

How Dangerous are Kilonovae?

An illustration of the kilonova GW170817. Credit: NASA/CXC/M.Weiss

When we look up at the sky on a particularly dark night, there is a sense of timelessness. We might see the flash of a meteor, and occasionally a comet is visible to the naked eye, but the cold and distant stars are unchanging. Or so it seems. There can also be a sense of calm, that despite all the uncertainty of the world, the stars will always watch over us. So it’s hard to imagine that light years away there could be a lurking event that poses an existential threat to humanity. That threat is extremely tiny, but not zero, and it is the focus of a recent paper published in The Astrophysical Journal.

January 28, 2024January 28, 2024 by Brian Koberlein

New Types of Hidden Stars Seen for the First Time

Artist’s impression of a cloud of smoke and dust being thrown out by a red giant star. Credit: Philip Lucas/University of Hertfordshire

In the early days of telescopic astronomy, you could only focus on one small region of the sky at a time. Careful observations had to be done by hand, and so much of the breakthrough work centered around a particular object in the sky. A nebula or galaxy, quasar or pulsar. But over the years we’ve been able to build telescopes capable of capturing a wide patch of sky all at once, and with automation, we can now map the entire sky. Early sky surveys took years to complete, but many modern sky surveys can look for changes on the order of weeks or days. This ability to watch for changes across the sky is changing the way we do astronomy, and it is beginning to yield some interesting results. As a case in point, an infrared sky survey is revealing hidden stars we hadn’t noticed before.

January 26, 2024January 26, 2024 by Brian Koberlein

Nancy Grace Roman Could Find the First Stars in the Universe

Simulation of a star ripped apart in a tidal disruption event. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR)

In the beginning, the Universe was so hot and so dense that light could not travel far. Photons were emitted, scattered, and absorbed as quickly as the photons in the heart of the brightest stars. But in time the cosmos expanded and cooled to the point that it became transparent, and the birthglow of the Big Bang could traverse space and time for billions of years. We still see it as the microwave cosmic background. As the Universe expanded it grew dark, filled only with warm clouds of hydrogen and helium. In time those clouds collapsed to form the first stars, and light again filled the heavens.

January 19, 2024January 19, 2024 by Evan Gough

Is this the Lightest Black Hole or Heaviest Neutron Star?

An international team of astronomers have found a new and unknown object in the Milky Way that is heavier than the heaviest neutron stars known and yet simultaneously lighter than the lightest black holes known. Image Credit: University of Manchester/Max Planck Institutue for Radio Astronomy

About 40,000 light-years away, a rapidly spinning object has a companion that’s confounding astronomers. It’s heavier than the heaviest neutron stars, yet at the same time, it’s lighter than the lightest black holes. Measurements place it in the so-called black hole mass gap, an observed gap in the stellar population between two to five solar masses. There appear to be no neutron stars larger than two solar masses and no black holes smaller than five solar masses.

January 19, 2024January 19, 2024 by Evan Gough

Astronomers See Massive Stars Forming Together in Multiple Star Systems

This false-color image of the massive star formation region G333.23–0.06 came from data obtained with the ALMA radio observatory. The insets show regions where researchers detected multiple systems of protostars. The star symbols indicate the location of each newly forming star. Image Credit: S. Li, MPIA / J. Neidel, MPIA Graphics Department / Data: ALMA Observatory

All stars form in giant molecular clouds of hydrogen. But some stars are extraordinarily massive; the most massive one we know of is about 200 times more massive than the Sun. How do these stars gain so much mass?

Part of the answer is that they form in multiple star systems.

January 10, 2024January 10, 2024 by Evan Gough

A Giant Star is Fading Away. But First, it Had an Enormous Eruption

Astronomers from Georgia State University’s CHARA Array have captured the first close-up images of a massive star known as RW Cephei that recently experienced a strange fading event. The images are providing new clues about what’s happening around the massive star approximately 16,000 light years from Earth. Image Credit: GSU/CHARA, Anugu et al. 2023

About 16,000 light-years away, a massive star experienced an unusual dimming event. This can happen in binary stars when one star passes in front of the other. It can also be due to intrinsic reasons like innate variability. But this star dimmed by as much as one-third, a huge amount.

What happened?

January 4, 2024January 4, 2024 by Evan Gough

This Globular Cluster is Plunging Toward the Milky Way’s Centre

The galactic cenre is dominated by powerful tidal forces. What happens to globular clusters that get too close? Image Credit: Spitzer Space Telescope/NASA/JPL-Caltech

Globular clusters (GCs) are spherical groups of stars held together by mutual gravity. Large ones can have millions of stars, and the stars tend to be older and have lower metallicity. The Milky Way contains more than 200 globulars, possibly many more, and most of them are in the galaxy’s halo, the outer reaches of the galaxy.

But they’re not all in the halo, and astronomers are keen to find ones nearest the galactic centre. Now, researchers have found one GC that’s plunging toward the Milky Way’s Centre.