Stars Archives

August 13, 2022August 13, 2022 by Carolyn Collins Petersen

In Wildly Different Environments, Stars End Up Roughly the Same

When you look at a region of the sky where stars are born, you see a cloud of gas and dust and a bunch of stars. It’s really a beautiful sight. In most places, the stars all end up being about the same mass. That mass is probably the most important factor you want to know about it. It directs how long the star will live and what its future will be like. But, what determines its mass and the mass of its siblings in a stellar nursery? Is there some governing force that tells them how massive they’ll be? It turns out that the stars do it for themselves.

August 12, 2022August 12, 2022 by Matt Williams

Why Betelgeuse Dimmed

Credit: NASA, ESA, and E. Wheatley (STScI)

Betelgeuse, the big reddish star that is the second brightest point in the constellation Orion (after Rigel), has been puzzling astronomers for years. Starting in October 2019, Belegeuse began to dim considerably, eventually reaching 1/3rd of its normal brightness a few months later. And then, just as mysteriously, it began to brighten again and (as of February 2022) has remained in a normal brightness range. The most likely reason appeared to be a circumstellar dust cloud rather than any changes in the star’s intrinsic brightness.

Using data from NASA’s Hubble Space Telescope (HST) and several other observatories, astronomers have concluded that a Surface Mass Ejection (SME) was the culprit. This event occurred in 2019 when Betelgeuse released a substantial mass of material that cooled to form a circumsolar dust ring, obscuring the star. In contrast to what regularly happens with our Sun during a Coronal Mass Ejections (CME), Betelgeuse ejected roughly 400 billion times as much mass as a typical CME. This is the first time something of this nature has been seen in a normal star’s behavior.

July 30, 2022July 30, 2022 by Brian Koberlein

When Stars eat Their Planets, the Carnage can be Seen Billions of Years Later

Artist view of a large planet soon to be devoured by its star. Credit: NASA, ESA, and G. Bacon (STScI). Science Credit: NASA, ESA, and C. Haswell (The Open University, UK)

The vast majority of stars have planets. We know that from observations of exoplanetary systems. We also know some stars don’t have planets, and perhaps they never had planets. This raises an interesting question. Suppose we see an old star that has no planets. How do we know if ever did? Maybe the star lost its planets during a close approach by another star, or maybe the planets spiraled inward and were consumed like Chronos eating his children. How could we possibly tell? A recent study on the arXiv answers half that question.

July 28, 2022July 28, 2022 by Brian Koberlein

A Fast-Moving Star is Colliding With Interstellar gas, Creating a Spectacular bow Shock

A multi-wavelength view of Zeta Ophiuchi. Credit: X-ray: NASA/CXC/Dublin Inst. Advanced Studies/S. Green et al.; Infrared: NASA/JPL/Spitzer

Zeta Ophiuchi has had an interesting life. It began as a typical large star about twenty times more massive than the Sun. It spent its days happily orbiting a large companion star until its companion exploded as a supernova about a million years ago. The explosion ejected Zeta Ophiuchi, so now it is speeding away through interstellar space. Of course, the supernova also expelled the outer layers of the companion star, so rather than empty space, our plucky star is speeding through the remnant gas as well. As they say on Facebook, it’s complicated. And that’s great news for astronomers, as a recent study shows.

July 22, 2022July 22, 2022 by Evan Gough

Astronomers Have a New Way to Find Exoplanets in Cataclysmic Binary Systems

Artist’s impression of a cataclysmic variable system as seen from the surface of an orbiting planet Credit Departamento de Imagen y Difusion FIME-UANL/ Lic. Debahni Selene Lopez Morales D.R. 2022 Licence type Attribution-NonCommercial-NoDerivs (CC BY-NC-ND 4.0)

Have you heard of LU Camelopardalis, QZ Serpentis, V1007 Herculis and BK Lyncis? No, they’re not members of a boy band in ancient Rome. They’re Cataclysmic Variables, binary stars that are so close together one star draws material from its sibling. This causes the pair to vary wildly in brightness.

Can planets exist in this chaotic environment? Can we spot them? A new study answers yes to both.

July 20, 2022July 20, 2022 by Carolyn Collins Petersen

A Dormant Black Hole has Been Discovered Just Outside the Milky Way

What happens when a massive star dies? Conventional wisdom (and observational evidence) say that it can collapse to form a “stellar-mass” black hole. Astronomers detect black holes by the X-ray emissions they emit.

But, what if the black hole isn’t giving off high levels of X-ray emissions? Then, it could be a very rare object indeed: a dormant black hole. Not many of these have been seen. So, it’s exciting to know that a team of astronomers has found one. It’s called VFTS 243. They detected it in Very Large Telescope observations of stars in the Tarantula Nebula, in the neighboring Large Magellanic Cloud.

July 6, 2022July 6, 2022 by Carolyn Collins Petersen

One Star Flies Past the Milky Way’s Black Hole at 3% the Speed of Light

Orbits of stars near Sagittarius A*. Credit: ESO/M. Parsa/L. Calçada

There’s a population of stars in the heart of our galaxy whipping around Sagittarius A* (the Milky Way’s central supermassive black hole). Astronomers just found the closest, fastest one (so far). It’s called S4716 and it orbits Sag A* once every four years. That makes it officially the fastest star moving at the heart of our galaxy. To give you some perspective, the Sun moves around the center of the galaxy at a much more leisurely pace once every 230 million years.

June 30, 2022June 30, 2022 by Carolyn Collins Petersen

Red Supergiant Stars Bubble and Froth so Much That Their Position in the Sky Seems to Dance Around

This artist’s impression shows the red supergiant star. Using ESO’s Very Large Telescope Interferometer, an international team of astronomers have constructed the most detailed image ever of this, or any star other than the Sun. Credit: ESO/M. Kornmesser

Making a 3D map of our galaxy would be easier if some stars behaved long enough to get good distances to them. However, red supergiants are the frisky kids on the block when it comes to pinning down their exact locations. That’s because they appear to dance around, which makes pinpointing their place in space difficult. That wobble is a feature, not a bug of these massive old stars and scientists want to understand why.

So, as with other challenging objects in the galaxy, astronomers have turned to computer models to figure out why. In addition, they are using Gaia mission position measurements to get a handle on why red supergiants appear to dance.

Artist’s impression of the red supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. It shows a boiling surface and material shed by the star as it ages. Credit: ESO/L.Calçada

June 30, 2022June 30, 2022 by Evan Gough

This is How You Get Multiple Star Systems

G205.46-14.56 clump located in Orion molecular cloud complex. The yellow contours stand for the dense cores discovered by JCMT, and the zoomed-in pictures shows the 1.3mm continuum emission of ALMA observation. These observations give insight into the formation of various stellar systems in dense cores. Image Credit: Qiuyi Luo et al. 2022.

Stars form inside massive clouds of gas and dust called molecular clouds. The Nebular Hypothesis explains how that happens. According to that hypothesis, dense cores inside those clouds of hydrogen collapse due to instability and form stars. The Nebular Hypothesis is much more detailed than that short version, but that’s the basic idea.

The problem is that it only explains how single stars form. But about half of the Milky Way’s stars are binary pairs or multiple stars. The Nebular Hypothesis doesn’t clearly explain how those stars form.

June 28, 2022June 28, 2022 by Nancy Atkinson

A Star has Grown Spiral Arms

Protostellar disk around a star at the galactic center. Image credit: Lu et al.

Astronomers using the ALMA Observatory have discovered an unusual, massive star near the center of our galaxy, a star that has two spiral arms. The arms are part of an accretion disk, a broad disk of dust and gas surrounding the protostar. While this is not the first star to be seen with such rare arm-like features, researchers say they believe they can track the formation of the spiral arms to a close encounter the star had with another object.