Connect with us

Space

First exoplanet discovered in another galaxy

First exoplanet discovered in another galaxy 86

The Chandra X-ray Space Telescope has found the first potential exoplanet in another galaxy. The planet orbits in a binary star system in a galaxy 23 million light-years away and was discovered by the eclipse of its star, a compact, ultra-powerful X-ray source.

A new method for searching for exoplanets, which is also suitable for studying other galaxies, is to register a decrease in the brightness of powerful X-ray sources (degenerate stars), which is caused by the transit of the planet. Thus, it was possible to detect the object M51-ULS-1b in the spiral galaxy M51 (the “Whirlpool” galaxy in the constellation of the Dog Hounds), which may be a gas giant or a brown dwarf in the X-ray binary system. An article by astronomers at the Harvard-Smithsonian Center for Astrophysics about this possible discovery appeared in September 2020 and is still available as a preprint at arXiv.org; it will probably be published later in the Monthly Notices of the Royal Astronomical Society (MNRAS).

The Whirlpool Galaxy, or M51, is a spiral galaxy 23 million light years distant. It is distinguishable through binoculars (apparent stellar magnitude about + 8ᵐ), and it is easy to find it in the northern sky near the extreme star of the Big Dipper bucket, although formally the site belongs to the neighboring constellation of Hounds.

It is one of the first extragalactic objects to be photographed in the middle of the 19th century. The galaxy has a companion – the neighboring dwarf galaxy NGC 5195, which it gradually eats, so a pair of galaxies looks spectacular in the pictures. It is assumed that the painting by Van Gogh “Starry Night” depicts this very object, which was then well known for publishing astronomical sketches in magazines.

First exoplanet discovered in another galaxy 87
The Maelstrom nebula (possibly) in a painting by Van Gogh (1889).

Extragalactic planets are objects in star systems or lonely planets outside our Galaxy. Most of the about 6,000 exoplanets discovered today orbit around stars at distances of up to hundreds of light years, that is, they belong to the nearest galactic environs. 

More distant stars, even within the Galaxy, are beyond the scope of studying their planetary systems. Moreover, this applies to objects in other galaxies at distances of millions of light years (for example, the distance to the center of our Galaxy is 25 thousand light years, and the nearest giant galaxy Andromeda is located at a distance of 2.5 million light years). Nevertheless, several extragalactic candidate planets are known. 

They were all discovered by the method of gravitational microlensing (distortion of the trajectory of light rays from a distant light source in the gravitational field of a star and its planetary system). 

This is an indirect method, and at extragalactic distances there is practically no possibility to independently confirm the discovery of an exoplanet by other means. Object M51-ULS-1b became the first extragalactic planet, which was discovered by the method of transit, standard for the study of “near” exoplanets – observations of periodic “eclipses” by the planet of its star in the process of moving in orbit. 

The transit method is one of two popular methods for exploring nearby exoplanets, along with the radial velocity method. Currently, the TESS space telescope is in orbit, the main task of which is to monitor several thousand of the nearest stars in the entire celestial sphere and search for their planets in this way (for more details about this NASA project, there is a separate article on our website). 

A similar problem was previously solved by the Kepler space telescope, which has already completed its work. The main difference between the two projects is that TESS monitors almost the entire sky sector-by-sector, exploring stars at distances of up to 100-200 light years, while Kepler focused on a small area, but captured stars at distances of up to 3 thousand light years (there is also note on the site). 

But extragalactic distances are orders of magnitude greater, and precise observations of the brightness of ordinary stars even in neighboring galaxies are not yet possible. 

Therefore, only superbright objects are suitable for research in other galaxies (not necessarily stars that are bright in the optical range). So far, these are X-ray sources, which are most often binary systems, where a compact object (black hole or neutron star) actively absorbs the matter of the companion star.

First exoplanet discovered in another galaxy 88
X-ray image of the galaxy M51 by the Chandra telescope and the position of the X-ray source M 51-ULS at the edge of the young star cluster in a detailed Hubble image. Di Stefano et al. (2020).


There can be up to several hundred such objects in galaxies. In the above Chandra image of M51 (left), they appear as bright dots. If the system contains a large exoplanet, then it can cause a short-term full or partial drop in the brightness of the source in the X-ray range, similar to the optical transit that telescopes can track.

 The very first exoplanets discovered in the mid-1990s in our Galaxy were also found near such exotic objects. Subsequently, when the number of exoplanets began to be measured in thousands, interest for obvious reasons shifted to planets in star systems similar to the Sun (or even better – in their “zones of potential habitability” and preferably closer, for example, near Proxima Centauri).

A group at the Harvard-Smithsonian Center for Astrophysics searched for transit events among 2,624 archived light curves for more than two hundred X-ray sources in spiral galaxies M51 , M101, and  M104, according to the Chandra orbiting telescope . 

Two other objects here are also familiar to astrolamists – these are the photogenic galaxies “Pinwheel” in Ursa Major (M101) and “Sombrero” in Virgo (M104), well oriented for observations in relation to us. One of the cases found is in good agreement with the light curve in the single transit model. It belongs to the X-ray source designated M51-ULS-1 – a young massive binary system closer to the outskirts of the galaxy M51. 

The object that caused the source to completely darken for 20-30 minutes could theoretically belong to several classes, including rocky or gas planets, as well as stars – white dwarfs or M-class stars (ordinary stars are red dwarfs). 

The properties of the light curve, according to the authors, exclude the “stellar” nature of this object, which received the “exoplanetary” designation M51-ULS-1b… It is assumed that it is slightly smaller than Saturn and may be a hot gas giant or a substellar object – a brown dwarf. It moves in an orbit of a large radius (according to estimates – tens of astronomical units) and at one time survived a supernova explosion in this binary system, which led to the formation of a compact X-ray object. 

The authors of the work suggest that the method can be used to search for exoplanets both in other galaxies and in the Milky Way, and its accuracy will increase with the quality of data from orbiting telescopes.

Whirlpool Galaxy M51 and companion by Hubble
Galaxies M51 (“Whirlpool”) and NGC 5195 – image from the Hubble telescope . NASA / ESA / STScI .

Comments

Space

KOI-5Ab, the curious planet that orbits in a system of three suns

KOI-5Ab, the curious planet that orbits in a system of three suns 89
Photo: (Caltech / R. Hurt (IPAC))

To us, the Sun alone seems perfectly normal, but our solar system is actually a strange exception.

Most stars in the Milky Way galaxy have at least one companion star. In a system 1,800 light-years away, astronomers have finally confirmed the existence of a gas giant planet orbiting stars in a triple star system.

Called KOI-5, the system is located in the constellation Cygnus, and the exoplanet was confirmed ten years after it was first detected by the Kepler space telescope.

In fact, the planet – now known as KOI-5Ab – was discovered by Kepler when it began operations back in 2009.

“KOI-5Ab was dropped because it was difficult and we had thousands of other candidates,” astronomer David Siardi of NASA’s Exoplanet Science Institute said.

“There were lighter dives than the KOI-5Ab, and every day we learned something new from Kepler, so the KOI-5 was almost forgotten.”

Exoplanet hunters tend to avoid the complexities of multi-star systems; of the more than 4,300 exoplanets confirmed to date, less than 10 percent are multi-star systems, although such systems dominate the galaxy. As a result, little is known about the properties of exoplanets in multi-star systems compared to those orbiting a lone star.

After Kepler’s discovery, Chardy and other astronomers used ground-based telescopes such as the Palomar Observatory, Keck Observatory, and the Gemini North Telescope to study the system. By 2014, they had identified two companion stars, KOI-5B and KOI-5C.

Scientists were able to establish that the planet KOI-5Ab, is a gas giant that is about half the mass of Saturn and 7 times the size of Earth, and is in a very close five-day orbit around KOI-5A. KOI-5A and KOI-5B, both of roughly the same mass as the Sun, form a relatively close binary system with an orbital period of about 30 years.

KOI-5Ab, the curious planet that orbits in a system of three suns 90

A third star, KOI-5C, orbits the binary system at a much greater distance, with a period of about 400 years – slightly longer than Pluto’s 248-year orbit.

“By studying this system in more detail, perhaps we can understand how planets are created in the universe.”

The discovery was announced at the 237th meeting of the American Astronomical Society.

Continue Reading

Space

Why the universe does not fit into science

Why the universe does not fit into science 91
Photo: YouTube

Science can be compared to an artist painting what he has never seen, or to a writer describing other people’s travels: objects that he has never seen, places where he has never been. Sometimes such scientific “arts” turn out to be beautiful and interesting, but most of them will forever remain only theories, because they are beyond human capabilities.

In fact, science has the right only to speculate: how our universe appeared, how old it is, how many stars and other objects it contains.

Universe model

Why the universe does not fit into science 92

How many stars are there in the sky?

With an unarmed eye, a person can see about nine thousand stars in the sky in one cloudless and moonless night. And armed with binoculars or a telescope, much more – up to several million. However, this is much less than their true number in the universe. Indeed, only in our one galaxy (the Milky Way) there are about 400 billion stars. The exact amount, of course, is not known to science. And the visible universe contains about 170 billion galaxies.

It is worth clarifying that scientists can see the universe 46 billion light years deep in all directions. And the visible (observable) universe includes the space accessible to our eyes from the moment of the Big Explosion. In other words, only this (accessible to human perception) space science refers to our universe. Science does not consider everything that follows.

It is believed that there are supposedly a ceptillion (10 to 24 degrees) stars in our universe. These are theoretical calculations based on the approximate size and age of the universe. The origin of the universe is explained by the Big Bang theory. This is why the universe is constantly expanding and the more time passes, the more complex the universe and its components become.

Why the universe does not fit into science 93

It is not entirely correct to consider and perceive this scientific theory “head-on”. Scientists always claim that that explosion was not exactly an explosion, and the point that exploded was not the only one. After all, it was everywhere, because space did not exist then. And in general – everything happened quite differently from what is described in the Big Bang theory, but all other descriptions of the origin of the universe are even more incredible and inaccurate.

Separate but interconnected

That which is beyond the reach of human perception is usually discarded by science, or recognized as non-existent. Recognizing one thing, science does not want to recognize the existence of the other, although everything in our world is interconnected and is not able to exist separately – by itself.

Each object of the universe is a part of it much more than an independent, separate object.

Any person, like any material object of our world, consists of components: organs, cells, molecules, atoms. And each of its constituent parts can represent the whole world. Separate, and at the same time connected with all the others.

However, science, as a rule, perceives all the components of the universe – people, animals, plants, objects, the Earth, the Sun, other planets and stars – as separate subjects, thereby limiting itself.

Why the universe does not fit into science 94

Even what is considered the visible universe, one of the atoms of which could be called our solar system, is not subject to the boundaries of human perception. But perhaps the atom is an exaggeration, and our solar system is not even an atom, but one of its elements!

How, being so far from the truth, can one reason about something with the degree of probability with which science tries to reason about the origin of the universe?

Continue Reading

Space

An unexplained wobble shifts the poles of Mars

An unexplained wobble shifts the poles of Mars 95

The red planet sways from side to side like a whirligig when it loses speed. The new study allowed scientists to notice that the poles of Mars deviate slightly from the axis of rotation of the planet. On average, they move 10 cm from the center with a period of 200 days.

Such changes are called the Chandler Oscillations  – after the American astronomer Seth Chandler, who discovered them in 1891. Previously, they were only seen on Earth. It is known that the displacement of the poles of rotation of our planet occurs with a period of 433 days, while the amplitude reaches 15 meters. There is no exact answer why this is happening. It is believed that the fluctuations are influenced by processes in the ocean and the Earth’s atmosphere.

Chandler’s wobbles on Mars are equally perplexing. The authors of the study discovered them by comparing data from 18 years of studying the planet. The information was obtained thanks to three spacecraft that orbit the Red Planet: Mars Odyssey, Mars Reconnaissance Orbiter and Mars Global Surveyor. 

Since Mars has no oceans, it is likely that the Red Planet’s wobbly rotation is due to changes in atmospheric pressure. This is the first explanation that researchers have shared. In the future, there should be new details about the fluctuations that have so interested the scientific community.

Continue Reading
Advertisement

DO NOT MISS

Trending