#astronomy Meet Gacrux, the High of the Cross – Sky & Telescope

May 30, 2021 - Comment

Gacrux Vitals Official title (IAU-approved)GacruxDifferent designationsGamma Crucis, HIP 61084, HR 4763, HD 108903NicknamesRubidea (in Brazil)Obvious magnitude1.64Distance from Earth88.6 light-yearsSortCrimson big, M3.5IIIColorationCrimson/orangeMass~1.three M☉Radius~120 R☉ConstellationCruxProper ascension12h 31m 10sDeclination-57° 06′ 48″A number of system?NoVariable star?SureExoplanets standingNone recognizedPossible destinyPlanetary nebula/white dwarf Bodily Traits On this installment of Meet the Stars, we make a journey to the southern skies and


Gacrux Vitals

Official title (IAU-approved)GacruxDifferent designationsGamma Crucis, HIP 61084, HR 4763, HD 108903NicknamesRubidea (in Brazil)Obvious magnitude1.64Distance from Earth88.6 light-yearsSortCrimson big, M3.5IIIColorationCrimson/orangeMass~1.three M☉Radius~120 R☉ConstellationCruxProper ascension12h 31m 10sDeclination-57° 06′ 48″A number of system?NoVariable star?SureExoplanets standingNone recognizedPossible destinyPlanetary nebula/white dwarf

Bodily Traits

On this installment of Meet the Stars, we make a journey to the southern skies and study Gacrux, a pink big star in one of many brightest and beloved asterisms — the Southern Cross.

This wide-field picture reveals a stretch of the Milky Approach seen from the Southern Hemisphere. At heart is Crux, the Southern Cross. The intense yellow-white star at far left is Alpha Centauri, which is definitely a three-star system. The Carina Nebula (NGC 3372) glows in pink on the proper of the picture.
Akira Fujii

Of the 4 predominant stars that make up the Southern Cross, Gacrux is the one pink member of the group, a undeniable fact that stands out clearly in long-exposure images. Its nice pink shade contrasts properly with the blue-white colours of the opposite stars within the Cross. The impact is much like the Betelgeuse’s standout shade in Orion (although Gacrux is a a lot smaller pink big).

Many huge stars are fairly distant, usually within the vary of a whole lot or hundreds of light-years away from Earth. Gacrux is considerably uncommon in that it’s solely about 88 light-years away — the closest pink big to Earth. Gacrux has a diameter 120 occasions the Solar’s, nevertheless it solely has about 30% extra mass. Like different pink giants, Gacrux is big however pretty diffuse. When the star started utilizing up its gas reserves, the fuel throughout the star cooled and expanded, a course of that can proceed as Gacrux advances in its stellar improvement.

Origin / Mythology

The Southern Cross is an excellent object, however one that’s largely absent from Western mythology. Although as soon as seen from the Northern Hemisphere, precession, the wobbling development of Earth’s axis that takes place over hundreds of years, slowly shifted the Southern Cross out of view; by round 400 AD it was out of sight and out of thoughts. (Earlier than it slipped over the horizon, the Greeks thought of the Southern Cross stars a part of Centaurus.) Europeans rediscovered the Southern Cross by the 1500s. Its fashionable title is attributed to French cartogropher Augustine Royer, who printed maps of the southern sky in 1679, although the constellation appeared in earlier maps too. The title might be a Christian reference.

In fact, whereas the Southern Cross was misplaced from northern view, it remained outstanding and vital in southern areas, with all kinds of tales related to it. The fishing communities in northern Australia, for instance, noticed the Southern Cross as a stingray, whereas within the desert areas of central Australia, aboriginals noticed within the constellation the observe of an eagle. To the Incas, the Southern Cross could have been a “chakana,” (bridge or crossing). A carved stone at Machu Picchu in Peru may characterize the Southern Cross.

Right now, the Southern Cross seems prominently on the nationwide flags of Australia, New Zealand, Brazil, Papua New Guinea, and Samoa.

The title Gacrux seems to be a contraction of Gamma Crux, from the Latin designation indicating it because the third-brightest star within the constellation. It’s a strictly utilitarian title, like Alpha Centauri.

Methods to See Gacrux

southern sky over San PedroThis wide-angle view of the sky over Chile reveals the Southern Cross at left, the darkish Coal Sack subsequent to it, and the stream of the Milky Approach passing via it. The Massive and Small Magellanic Clouds adorn the sky at proper.
J. Kelly Beatty / S&T

You have to be south of 25°N latitude to see the whole Southern Cross, so it’s just about unattainable to view from the continental U.S. It’s doable to a catch glimpse of Gacrux from the acute southernmost parts, just like the Florida Keys, however catching Gacrux because it briefly pops over the horizon requires a superbly clear view to the south and exact timing. (Gacrux is the constellation’s northernmost star and subsequently the most definitely one to see.)

A greater plan for viewing the Southern Cross from the U.S. could be a visit to Hawai‘i. The island chain lies slightly below 25°N, so the constellation is seen in its entirety throughout winter and spring. Even nonetheless, the Southern Cross hangs fairly low within the south and solely rises for a few hours earlier than diving again under the horizon.

For the perfect views of Gacrux, you’ll have to get into the Southern Hemisphere. (They don’t name it the “Southern Cross” for nothing!) Massive parts of South America, Africa, and Australia will present the Cross completely, and in case you go under 35°S, the Cross turns into circumpolar, staying up all evening, similar to Cassiopeia does within the north.

There isn’t a handy south pole star — no Polaris counterpart exists in that portion of the sky — however the Cross can be utilized as a pointer. An imaginary line from Gacrux via Acrux (the constellation’s southernmost star) factors roughly on the celestial south pole.

Seeing Gacrux and the Southern Cross is nothing uncommon for residents of the Southern Hemisphere, however for guests who’ve by no means seen these objects, they are often the spotlight of a visit. When you’re there, ensure to take a look at the Coalsack Nebula inside Crux and the Magellanic Clouds (the Milky Approach’s miniature companion galaxies) too.

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