is there an app to identify stars?

If you want to point your phone and name a star

Stellarium Mobile is the closest match. Its page says sensor control can identify a star in a few seconds when you point the phone at the sky. It names planets and satellites too, including the International Space Station, and it works on iPhone and Android.

The catch is cost. The vendor page describes a base app and an upgrade to Plus, but it gives no price and does not call the base app free. Whether the base app is free is not verified, so check the store listing before you download.

If you want a catalogue that goes deep

Stellarium Mobile again. Its page lists the Gaia DR2 catalogue of over 1.4 billion stars, plus over 3 million nebulae and galaxies. If you only want to know what the bright dot above the garden is, that depth will not matter much. If you go back out regularly and look for fainter objects, it gives you more to find.

If you have an iPhone and want Siri to name things

Sky Guide is the one for this. Its page says you can ask Siri what star that is, or point an iPhone at a bright star, planet or satellite and have Sky Guide identify it from the home screen through Siri Shortcuts. It also has a calendar of sky events and a red night mode, which helps once your eyes have adjusted to the dark.

It is for Apple devices only. The page lists iPhone, iPad and Apple Watch, and there is no Android version on it. The page mentions family sharing and educational discounts but gives no price, so whether it has a free tier is not verified.

If you want a star map with no install

Stellarium Web is an online star map that runs in the browser. It has toggles for constellations, constellation art, atmosphere, landscape, deep sky objects and night mode, so you can open it on any device with a browser and look up the sky.

Its page did not say whether it identifies objects when you point a phone at the sky, so treat it as a map you read rather than a pointer you aim. It also states no price or free tier, so both are not verified.

If you want a sky map with an encyclopedia on Android or iPhone

Star Walk 2 has a store listing for both iPhone and Android. Its site quotes a review saying it identifies the location of stars, planets, meteors and nebulae, the International Space Station and comets, which is a wide range of objects.

Those words come from a quoted press review, not from the vendor. Read the store description to see what the app itself says it does. The site's store links point to a package named Star Walk 2 Free, but the page states no free tier or price, so that is not verified either.

When paying is worth it

Stellarium says its Plus version is for advanced users and adds telescope control, an ocular view, observation tools, a calendar and a 3D view, which its comparison table shows the base app without. For naming stars with your phone, the base features listed on its page may be enough. What Plus costs is not verified, because the vendor page gives no price.

None of the four vendor pages states a price. Check the store listing for the current price and any subscription before you download, not after.

Pointing a phone at the sky depends on its sensors. Stellarium's page describes the feature as sensor control, so how well it works will depend on your phone. We did not test this.

Star Walk 2's identification wording on its site comes from a quoted press review. The store description is the better guide to what the app itself claims.